The present invention relates to a control apparatus for inverters, etc. and more particularly to the construction of a housing thereof.
In general, electrical circuit elements forming an inverter apparatus include elements for a main circuit and elements for a control circuit. The amount of heat generated from diodes, thyristers, transister modules, etc. as the elements of the main circuit is relativley large.
In the case of machinery having a large capacity the degree of heat loss can be as high as about 1 kW. Therefore, it is necessary to dissipate the generated heat through die cast fins of aluminum so as to be able to use the diodes, thyristors, transistor elements, etc. in their normal manner, and at the same time so as not to subject electronic elements of the control circuit provided on a printed circuit board to the effects of temperature thereby lengthening the life of the elements and increasing their reliability.
An example of an inverter as a conventional control apparatus of this type is shown in FIGS. 1 to 3 of the attached drawings. Within a chassis 2 of a control apparatus 1 having generally a rectangular cross-section are secured fins 4 of an aluminum die cast product. Fins 4 have mounted thereon semiconductor elements 3 for a main circuit, and are adapted to dissipate heat generated from semiconductor elements 3. For this purpose a fan 5 is mounted inside chassis 2 below radiating fins 4. Other elements 6 constituting circuits are also mounted within chassis 2. A panel 8 is hinged to chassis 2 by hinges 7 located at the upper and lower side portions, as viewed in FIG. 1 of the chassis so as to be opened and closed. A printed circuit board 9 is mounted on panel 8 by means of insulating spacers 10. The above described elements are wired together according to particular circuit diagrams.
Upon operation of the inverter apparatus, main circuit electrical elements 3 generate heat that is transfered to radiating fins 4, the temperature of which is raised. However, due to the fan 5 located below fins 4, air passes through and strikes the fins. Thus, the temperature of the fins is lowered and the semiconductor elements 3 for the main electrical circuit are maintained within a predetermined temperature range. However, in this case a problem arises involving the external dimension of the chassis or housing 2 required to contain the apparatus, i.e. to provide the necessary internal volume of the housing. The inner volume of the housing must be sufficiently large for the heat generated from the inventor apparatus as a whole to dissipate naturally through the outer surface of the housing so that the temperature within the housing is maintained within the predetermined temperature range of the components. However, in this conventional apparatus, since the housing is formed as stated above, when it is necessary to have the external dimension of the housing made large, it also is necessary to fabricate all of the housing components anew. Therefore, this has the disadvantages of making standardization of fabrication difficult. Further, since the heated air circulated by fan 5 imparts thermal effects to main circuit components 3 and other elements 6, the life and reliability thereof are decreased.